Conventionally, an X-ray diagnostic apparatus is known which irradiates radioactive rays such as X-rays at an object, detects the X-rays passing through the object, acquires projection data, and generates image data on the basis of the projection data.
The X-ray diagnostic apparatus includes an X-ray tube capable of firing X-rays, and a movable diaphragm, which limits an irradiation area of X-rays to spare the object from excessive exposure to radiation is disposed on a front surface of the X-ray tube. The movable diaphragm can set an X-ray irradiation field (irradiation area) to a desired region by adjusting an extent of opening of built-in diaphragm blades. To set the X-ray irradiation field, it is necessary to check the irradiation field on the object, and performing this check without actually firing X-rays is important.
Therefore, a movable diaphragm device and a radiographic apparatus have been proposed with which a clear X-ray irradiation field can be obtained as well as radiation conditions required for obtaining the same irradiation result can be relaxed.
In the X-ray diagnostic apparatus having a movable diaphragm, the movable diaphragm typically includes four diaphragm blades, and to set the X-ray irradiation field, the movable diaphragm moves each diaphragm blade in a horizontal direction relative to the X-ray tube so as to open/close an irradiation aperture.
However, since the movable diaphragm has such a structure that all the four diaphragm blades are opened to open the irradiation aperture, it is necessary to clear an area corresponding to the four diaphragm blades when fully opening the irradiation aperture.
In particular, since the movable diaphragm is often used in close contact with the object, securing a retraction space for retracting the diaphragm blades raises a problem that the size of the main body of the movable diaphragm increases.